Control for vehicle braking system



Aug. 1, 1950 J. G. CETZEL SONTROL FOR VEHICLE BRAKING SYSTEMS Original Filed May 2, 1942 W R a m H e V O m H W r W O Q G W .n O J ATTORNEYfi Patented Aug. 1, 1950 CONTROL FOR VEHICLE BRAKING SYSTEMS John George Oetzel, Beloit, Wis., assignor to Warner Electric Brake Manufacturing Company, South Beloit, 111., a corporation of Illinois Original application. May 2, 1942, Serial No. 441,436. Divided and this application January 25, 1946, Serial No. 643,322

3 Claims. 1

This invention relates to a control governing the automatic energization of electrodynamic brakes on an automotive vehicle.

One object is to provide a control for an electrodynamic brake including a vehicl'e drive'n generator and means for maintaining the generator disabled effectually at times when the brakes are to be deenergized. H

Another object is to provide an electrodynamic rake energized by a vehicle-driven generator under the control of the manually operable speed controller of the vehicle.

A further object is to provide anovel. means for maintaining thev electrodynamic braking means ineffectual below predetermined vehicle spee Other objects and advantages ofthe invention will become apparent from the following detailed descriptiontaken in connection with the accompanying drawings, in which Figure l is a plan view f the wheel and axle assemblies and the power plant of a truck equipped with a braking system embodying the present invention, the. truck bodybeing shown in phantom. V v

Fig, 2 is a schematic view and wiring diagram of the automatic control,

For purposes of illustration, th'e invention has been shown as applied to the control of v auxiliary I brakes in of the eddy current type applied to the axles of a truck or tractor H driven by an internal combustion engine .13. The brakes are of the well-known eddy current type comprising a non-rotatable toothed magnet core 14 adapted to be fixed to the axle housing 15 of the vehicle and having a winding 16' and arranged with the magnet poles coacting with a flange or drum ll, preferably composed of cast ironand driven in unison with the vehicle axle. When the winding i6 is energized, flux threads the, circuit, around the winding including the drum .or inductor l'l creating eddy currents in thelatter. Themagnet being stationary, a retardingeffect is thus exerted on the drum and therefore on the vehicle" axle, the magnitude otthis effect being proportional to the vehicle speed and'the energizing current.

Current for energizing the eddy current brake windings I6 is preferably derived by an electric generator 18 which may be mounted on the truck and driven as by a belt from the propeller shaft l9. For reasons to appear later, the generator is of the compound type having a shunt winding 20 and a series winding 2|, the latter producing a heavily predominant field.

the generator. indicated by lighting of a signal lamp 33 on the vehicle dash, occurs when the ignition switch is circuit. This switch is responsive to the vehicle speed and for this purpose may be actuated by a centrifugal device 25 comprising fiyweights 28 on a head 21 which may be driven from the gen- 'erator shaft 28. When the vehicle speed exceeds a predetermined value, for example, twenty-five miles an hour. below which gear shifting is usually effected, the flyweights move outwardly and shift a sleeve 29 against the action of a spring 3 sufficiently to hold the switch 24 closed. Below this selected speed, the switch is allowed to remain open and the circuit is disabled. Also included in the generator field circuit is the engine ignition switch 3| which operates to prevent draining of the battery 32 when the vehicle is not in use.

In the present instance. the switches 23, 24

and ii! are interposed in series in a circuit including the battery 32 and the shunt winding 20 of Energization of this winding, as

closed, when the vehicle is traveling above normal gear shifting speeds as evidenced by closure of the switch 24, and when the accelerator is fully retracted, the latter being the natural posi- "tion of the pedal during coasting of the vehicle.

The windings l6 of all of the eddy current brakes are'connected in parallel in a circuit which extends through the generator armature 34, the

series field winding 2! and the winding 35 of a ,relay switch 40. Effective energization of the brake windings l6 and the degree of such energization is controlled by shunts in parallel with the series winding 2| and the relay winding 35.

One of these includes a rheostat 3B which is adjustable to vary the degree of energization of the brake windings for a given output current of the generator and therefore the speed of the vehicle. This may, if desired, be located in the truck cab. A second one of the shunts includes a switch 31 normally closed by a spring 38 and opened by energization of a relay winding 39, which winding is in parallel with the shunt genresponse to such energization, the switch All is closed, the shunt causing a current decrease sufficient to reopen the switch. This process is repeated in rapid succession so that the relay and switch act as a regulator limiting the maximum current applied tothe eddy current brakes.

It will be observed that the circuit arrangement above described functions normally to maintain the eddy current brake windings energized continuously whenever the vehicle is coasting at a speed above that for which the centrifugal-switch 24 is adapted to respond and become closed. The energization will vary automatically with the vehicle speed producing an electrodynamic re-- tarding effect which increases with the vehicle speed and which may be varied in degree by adjustment of the rheostat 36. As a result, the vehicle speed will be maintained substantially constant on low down grades where all of the required retarding may be supplied by the auxiliary eddy current brakes alone. The speed thus held will be proportional to the grade which the vehicle is descending but will, due to the selected characteristics of the generator, always be near the value selected for safe driving. Except for very gradual grades, the speed thus acquired will usually be between thirty and forty miles per hour. If the established speed is less than that considered safe for driving, the driver may render the eddy current brakes ineffectual simply by depressing the accelerator pedal 22 sufficiently to open the switch 23. When the desired higher speed is attained, the pedal is again released to bring the eddy current brakes into action.

By adjustment of the above described shunt 36 and a shunt 4!, it will be apparent that the generator characteristics may be changed as desired. This is advantageous in adapting the eddy current braking to the prevailing vehicle load and the number of vehicles included in the train.

The adjustment enables the generator to be conditioned for producing a constant voltage at different amperages.

Now, if the vehicle comes to a long down grade,

the accelerator and proceed without shifting to a low gear. The shunt field of the generator will be excited immediately. If the vehicle is travel- ,cent, with brakes of the capacity described above,

the vehicle motion will be fully checked by the eddy current efiect alone and a speed will be the driver will, with the present control, release established at which the braking effect plus the engine friction at the prevailing gear ratio balance the gravitational force tending to accelerate the vehicle.

This application is a division of my co-pending application Serial No. 441,486, filed May 2, 1942, now Patent No. 2,395,904.

I claim as my invention:

1. A vehicle braking system having, in combination, an electric generator driven in unison with the vehicle motion and having a shunt winding and a series winding, means operable automatically during'coasting of said vehicle above a predetermined speed to energize said shunt winding, electrodynamic braking means variably energized by said generator, a magnetic relay having a winding in parallel with said shunt winding and a switch adapted to be opened when the relay winding is energized to a predetermined degree, and means providing a short circuit around said series windingand having said relay switch interposed therein.

2. In a vehicle braking system having, in combination, an electric generator adapted to be driven. in unison with the vehicle motion and having a shunt winding and a series winding, means operable automatically during coasting of said vehicle above a predetermined speed to energize said shunt winding, electrodynamic braking means variably energized by said generator, and means for maintaining a short circuit around said series field when said shunt winding is deenergized.

3. The combination with a vehicle having a manually operable controller movable away from an idling position to increase the vehicle speed, of a generator driven in unison with the vehicle motion, an electrodynamic brake for the vehicle energized by said generator in proportion to the vehicle speed, a speed detector responsive to changes in the speed of said vehicle and operable to detect rises and falls in the speed above and below a predetermined value, and switching mechanism actuated .by said vehicle speed controller and by said speed detector and operable to energizesaid brake from said generator when the vehicle speed increases above a predetermined value with said controller in said idle position and to maintain said brake deenergized either when said controller is out of said idle position or when the vehicle speed is below said'predetermined value.

JOHN GEORGE OETZEL.

R FERENCES CITED The following references are of record in the file of this patent:

UNITED s'r TEs PATENTS Number Date 577,119 Sperry Feb. 16, 1897 1,479,463 Entz Jan. 1, 1924 1,677,633 Harrison July 17, .1928 2,035,047 Cotter Mar. 24,1936 2,107,984, Harper Feb. ,8, 1938 2,266,213

Kattwinkel Dec. 16," 1941 

